1. Field of the Invention
The present invention relates to a transmitting device, and more particularly, to a transmitting device capable of solving distortion problems of output signals of a power amplifier and a method capable of determining a target predistortion setting value (i.e. an optimal predistortion setting value) from a plurality of candidate predistortion setting values, so as to solve the above problem.
2. Description of the Prior Art
In a wireless communication system, a transmitting device generally has a power amplifier at an output terminal to amplify a signal which is going to be transmitted and output the amplified signal. However, the power amplifier has a worse linearity when a larger power is inputted, and thus the amplified output signal has a distortion problem. In a prior art, a predistortion unit is positioned in a front stage of the power amplifier to compensate a non-linear effect of the power amplifier. Please refer to FIG. 1. FIG. 1 is a diagram showing characteristic curves of a predistortion unit 102, a power amplifier 104, and the amplitude/amplitude (AM/AM) characteristic curves thereof. As shown in FIG. 1, the linearity between an input signal power Pin and an output signal power Pout of the power amplifier 104 is better, and the data correctness of the output signal of the power amplifier 104 can be improved. In general, the predistortion unit and related method utilized to solve the distortion problem of the power amplifier of the transmitting device in the prior art requires complicated algorithms and high cost. Therefore, how to provide a transmitting device comprising a predistortion unit which is simple, efficient, and has lower cost and related method becomes an important issue.